NEW! We're excited to announce two new radiology learning pathways by Andrew Dixon and Frank Gaillard LEARN MORE

Neural tube defects

Neural tube defect (NTD) refers to the incomplete closure of the neural tube in very early pregnancy, resulting in cranial defects or spinal dysraphism.

The neural tube comprises of a bundle of nerve sheath which closes to form brain caudally and spinal cord rostrally. The closure should occur at around the 28th day of conception failing which the brain or spinal cord doesn't form properly.

Numerous types of neural tube defect are recognized including 5-6:

Neural tube defects affect approximately >1-11 out of 1000 pregnancies 4-6

Folic acid deficiency is one of the leading causes of anencephaly. By supplementing with folic acid in early pregnancy, this defect can be prevented. It is more prevalent in developing countries and in mothers of low socio-economic status.

  • maternal diabetes
  • maternal obesity 7
  • anti-epileptic use in pregnancy 8
  • elevated maternal serum alpha-fetoprotein (MSAFP) levels 
  • elevated amniotic fluid acetylcholinesterase (AChE) levels: in an open neural tube defect 3

These are different for each entity and best discussed under each subtype.

Most neural tube defects can be diagnosed by one of the following tests:

  • maternal serum alpha-fetoprotein (MSAFP): a screening test performed in the pregnant woman serum during 16-18 weeks of pregnancy (elevated)
  • amniocentesis: invasive procedure, performed during 15 weeks of pregnancy
  • antenatal ultrasound: allows detection of anencephaly/acrania at 12 weeks of pregnancy

Both the management and prognosis is heavily dependent on the type of neural tube defect. The risk for a subsequent pregnancy is thought to be ~5-10%.

Article information

rID: 7736
Synonyms or Alternate Spellings:
  • Neural tube defect
  • Craniospinal defects

ADVERTISEMENT: Supporters see fewers/no ads

Cases and figures

  • Case 1: anencephaly
    Drag here to reorder.
  • Case 2: spina bifida
    Drag here to reorder.
  • Updating… Please wait.

     Unable to process the form. Check for errors and try again.

     Thank you for updating your details.